Polyimides are known in the art for use in the manufacture of circuit assemblies such as integrated circuit chips and multichip modules. For example, Dawson et al. U.S. Pat. No. 5,420,232 discloses the use of a class of polyimides in the manufacture of electronic components. Polyimides are useful in forming dielectric layers, passivation layers, alpha particle barriers and stress buffers. Polyimides are also useful as a dielectric material to insulate the conductor wiring in multilayer circuit assemblies such as the back end of the line of integrated circuit chips and multichip modules. A multichip module is an intermediate level of packaging between the chips and the circuit board. Multichip modules are made up of a plurality of insulating and conducting layers wherein the conducting power, signal and ground layers deliver power to the chips and distribute the input/output signals between chips on the module or to/from the circuit board. Multichip modules typically contain input/output pins on the bottom surface for connection to the circuit board. Polyimides have also been utilized as insulating layers on integrated circuit chips especially in the back end of the line with the input/output circuitry of the chip. It is important that the polyimide have low and isotropic dielectric constant to avoid signal crosstalk. Also, it is important that the polyimide have improved planarization properties to enable it use on uneven substrates having uneven topography to provide a level surface for subsequent circuit formation. Further, the polyimide should have high thermal stability to enable the use of advanced processing techniques which operate at a higher temperature.
It is therefore an object of the present invention to provide an improved process for forming a circuit assembly with a unique class of polyimides.
Other objects and advantages will be apparent from the following disclosure.